Polyester films can be used in a variety of applications. In order to be suitable for various applications, the polyester materials should have corresponding functional requirements. For example, an upper layer and a lower layer of the back-sheet of a solar cell module are DuPont's Tedlar films, and a middle layer between the upper layer and the lower layer is a polyester film. Since solar cells are often in a humid and warm environment, materials used in solar cells should meet the weathering resistance requirements. Therefore, a polyester film of the back-sheet used in a solar cell has to exhibit a high weathering resistance (e.g. thermal resistance and hydrolysis resistance).
Accordingly, a polyester film with both good thermal resistance and hydrolysis resistance is still called for.